Friday, February 08, 2008

Heartbeat radar

The tiniest chest movements, caused by breathing and even the beating of the heart, can be monitored using doppler radar. Just like road-speed radar systems, this works by bouncing a radio wave off the chest and measuring any change in frequency caused by chest movement.

In theory, the technique could be very useful since it allows a patient to be monitored from a distance without fitting them with ECG leads. It can even record a heartrate through a person's clothing. But the signals can be easily swamped by noise caused by small movements of the patient or of other people around them, for example in a busy hospital ward.

Now Olga Boric-Lubecke, an electrical engineer at the University of Hawaii, US, has found a way to solve such problems.

She and colleagues have developed a radar device with several transmitters and receiving antennas that produce multiple signals that can be picked up and processed in a way that removes any random noise from other sources of movement.

The resulting signals are analysed by a computer to tease apart the various movements of a patient, including their heart beat and breathing pattern.